In conventional optical systems, such as in digital cameras, motors and solenoids are used as sources of power to displace gears and cams which act upon optical elements, e.g., lenses, to provide focusing, zoom, and image stabilization (also referred to as shake prevention). There are many disadvantages to such conventional systems—power consumption is high, response times are long, accuracy is limited and space requirements are high.
Advancements in miniaturized technologies have led to high-quality, highly-functioning, light-weight portable devices, and an ever-increasing consumer demand for even further improvements. An example of this is the development of cellular telephones to include a camera, often referred to as camera phones. While the majority of such camera phones employ an all-mechanical lens module having a small form factor lens, this approach does not offer variable or auto-focusing, zoom and image stabilization capabilities due to the significant number of moving parts required. For example, zoom capability requires a combination of lens elements, a motor, and a cam mechanism for transmitting the rotational movement of the motor to linear movement in order to adjust the relative positions of the lenses and an associated image sensor in order to obtain the desired magnification. In addition to the motor and cam mechanism, a plurality of reduction gears are is used to accurately control the relative positioning of the lenses.
Electromagnetic type actuators which include a coil generating a magnetic force where the magnet has a length longer than that of the coil in the optical axis direction (commonly referred to as “voice coils”) are commonly employed to perform many of the auto-focus and zoom actuator functions within digital still cameras and, to some extent, in camera phones. This voice coil technology has been widely accepted as it enables small and lighter optical lens systems. However, a downside to lighter and smaller cameras, particularly those with capabilities for longer exposure times and having higher resolution sensors, is the greater effect that camera shake, due primarily to hand jitter, has on the quality of photographs, i.e., causing blurring. To compensate for camera shake, gyroscopes are often used for image stabilization. A gyroscope measures pitch and yaw, however, it is not capable of measuring roll, i.e., rotation about the axis defined by the lens barrel. Conventionally, two single-axis piezoelectric or quartz gyroscopes have been used with many external components to achieve the full-scale range of image stabilization. InvenSense, Inc. provides an integrated dual-axis gyroscope using MEMS technology for image stabilization which offers smaller sizing.
While variable focusing, zoom and image stabilization features are possible within a camera phone and other optical systems having a relatively small form factor, these features add substantially to the overall mass of these devices. Further, due to the necessity of an extensive number of moving components, power consumption is significantly high and manufacturing costs are increased.
Accordingly, it would be advantageous to provide an optical lens system which overcomes the limitations of the prior art. It would be particularly advantageous to provide such a system whereby the arrangement of and the mechanical interface between a lens and its actuator structure were highly integrated so as to reduce the form factor as much as possible. It would be greatly beneficial if such an optical system involved a minimal number of mechanical components, thereby reducing the complexity and fabrication costs of the system.